He's become unhinged with hatred that he's been stewing in for every second of 10 years (315,360,000 seconds if anyone's curious); small wonder he's lost the vast majority of his softer emotions.
@Blaster746
Ainz-sama kills to protect the memento of his dearest friends which is the whole of the Tomb of Nazarick and their creations or children as how he likes to call them
Dweight kills for revenge and to create the world his dearest wished for even if it means destroying it to achieve it or more like
conquering it as is stated in the wn that he is actually stronger than the DM they fought in the past due to all the miasma that he absorbed.
Their methods I don't think are that different, just their motives.